Typically, two distinct types of drives, six-step trapezoidal drives and PWM drives, are used to drive multi-phase BLDC motors. In the six step trapezoidal drives, speed regulation is obtained by controlling a direct current (DC) supply voltage with a pre-regulator operating at a high frequency. In the PWM drives, the speed regulation is obtained by controlling a volt-seconds alternating current (AC) output. That is achieved by PWM of a DC supply voltage at a high frequency.
Several types of the six step brushless drives are commercially available. These drives are typified by a TDA5142T integrated circuit (IC) 10 from Philips Semiconductors shown in a BLDC motor drive circuit of FIG. 1. These ICs 10 directly drive the power insulated gate bipolar transistors (IGBTs) 14 connected to the BLDC motor 12.
Both types of drives, the six-step trapezoidal drives and the PWM drives, require power IGBTs capable of operating at high frequencies and, therefore, both types of drives have significant switch efficiency losses.
It is therefore an object of the present invention to provide a three-phase PWM BLDC motor drive circuit that minimizes switch efficiency losses of the IGBTs or other types of transistors operating at high frequencies.